(a) Field of the Invention
The present invention relates to an extended paging indicator-based adaptive discontinuous reception method for improving a power reduction performance in an asynchronous wideband code division multiple access method.
In detail, A radio resource control layer in a wireless network control apparatus or a base station performs scheduling and adaptively controlling a discontinuous reception cycle for a terminal of a power reduction mode. According to traffic characteristics, QoS, and a terminal power satate, a discontinuous reception cycle of the terminal is adaptively controlled through an extended paging indicator even though terminal is in the discontinuous reception operation. So will bring improvements in power reduction performance, transmission time delay, and transmission failure possibility with respect to the paging message and packet reception
(b) Description of the Related Art
Since the digital cellular-based second generation mobile communication system was launched, a third generation mobile communication system as an international mobile telecommunication 2000 (IMT-2000) has been standardized by the International Telecommunication Union (ITU) so as to support a high quality multimedia service without limiting area. Recently, as various specifications for the IMT-2000 system, the Universal Mobile Telecommunications System (UMTS) and the CDMA 2000 system completed by two large standardization organizations have been launched or prepared. The two large standardization organizations are Third Generation Partnership Projects (3GPP) and Third Generation Partnership Projects 2(3GPP2).
The asynchronous wideband code division multiple access(WCDMA) technology has been developed in the 3GPP so as to configure a future high speed packet data transmission network of the next generation mobile communication system. The asynchronous WCDMA system has progressed based on a network structure of a conventional GSM (Global System for Mobile communications) scheme, and it may be relatively easily synchronized between base stations and terminals. It advantageously configures such infrastructures as a base station installation in comparison with the IS-95 (Interim Standard-95) series of the conventional synchronous code division multiple access system (CDMA) based base station, and may tremendous marketability and growth potential of upwards of about 80% of the entire world market through capacity improvement.
Meanwhile, the next generation mobile communication network configured based on such a wideband code division multiple access system may have been expected to provide such various high quality multimedia data services that only the wire network had provided such as visual telephone, streaming, and VoD (Video on Demand) in a wireless and mobile environment. However, considering a user terminal, power consumption is rapidly increased and the lifetime of a terminal battery is decreased. If efficient power management for improving a power saving performance is not performed between the base station and the terminal, and all the terminal power is consumed before the user sufficiently receives various services supplied from the base station.
Accordingly, in order to reduce terminal power consumption, the next generation mobile communication service has focused on a method for increasing the terminal battery lifetime with an efficient power saving method through the minimizing of terminal power consumption by effectively stopping or controlling a terminal power supply during intermittent use or by not using a wireless communication link.
Accordingly, in order to save terminal power, the 3GPP specification for the wideband code division multiple access system may have three terminal power saving modes related to a radio resource control (RRC) layer, an idle mode and Cell_PCH and URA_PCH states of the connected mode, and it provides a paging message indication method through a discontinuous reception (DRX) of the paging indicator channel (PICH).
FIG. 1 is a block diagram for showing a cross-relation among an idle mode, a connected mode, a power saving mode for reducing terminal power, and a power active mode in a wideband code division multiple access system.
The paging indicator (PI) detection-based terminal power saving method is proposed by the present 3GPP specification, it uses the discontinuous reception cycle length in the power saving mode. Paging indicators occur on the corresponding physical channel, the paging indication channel(PICH). For each terminal, a paging indicator channel frame is referred to as a paging occasion (PO) block. The terminal that performs power saving through such discontinuous reception of paging indication has an allocated specified paging indicator position in the specified paging occasion block of the discontinuous reception cycle. It checks its paging indicator, and it then determines whether to return to a discontinuous reception process so as to save power or to convert to power active modes of Cell_FACH and Cell_DCH states, that is, the connected mode of FIG. 1, according to the existence or non-existence of the paging message for packet transmission/reception. Since such a method applies the same length of discontinuous reception cycles for all terminals performing power saving within the specified cells, the base station has a small load for the power saving. In addition, since the pluralities of terminals are evenly distributed, a false alarm probability with respect to the paging message reception of the terminals in cells may be reduced.
Hereinafter, a power saving method using a conventional discontinuous reception method in the wideband code division multiple access scheme will be described with reference to FIG. 2.
FIG. 2 illustrates periodic paging confirmation through a conventional fixed discontinuous reception method so as to save terminal power in a wideband code division multiple access method.
First, all the terminals performing power saving in a specified cell receive the same discontinuous reception cycle coefficient (DRX Cycle Length Coefficient) □ though system information broadcasting of the base station, and determine the discontinuous reception cycle through Equation 1.DRX Cycle Length=MAX(2k, PBP) [frames]  EQUATION 1
Herein, “PBP” indicates Paging Block Periodicity and is given as 1 in the case of the Frequency Division Duplexing (FDD)-based wideband code division multiple access schemes, and accordingly, a final discontinuous reception cycle become a 2k frames. Referring to the 3GPP specification, “□” is determined by one of integers 6, 7, 8, and 9, and accordingly the discontinuous reception cycle becomes 2k, that is, 64, 128, 256, and 512 frames. The paging occasion positions for the specified terminals in the given discontinuous reception cycle may be determined by Equation 2.
                              P          ⁢                                          ⁢          O                =                                                            [                                                      (                                          I                      ⁢                                                                                          ⁢                      M                      ⁢                                                                                          ⁢                      S                      ⁢                                                                                          ⁢                      I                      ⁢                                                                                          ⁢                      div                      ⁢                                                                                          ⁢                      K                                        )                                    ⁢                                      mod                    (                                          DRX                      ⁢                                                                                          ⁢                      Cycle                      ⁢                                                                                          ⁢                      Length                      ⁢                                                                                          ⁢                      div                      ⁢                                                                                          ⁢                      P                      ⁢                                                                                          ⁢                      B                      ⁢                                                                                          ⁢                      P                                        )                                                  ]                            ×              P              ⁢                                                          ⁢              B              ⁢                                                          ⁢              P                        +                          n              ×              D              ⁢                                                          ⁢              R              ⁢                                                          ⁢              X              ⁢                                                          ⁢              Cycle              ⁢                                                          ⁢              Length                        +                          Frame              ⁢                                                          ⁢              Offset                                ⁢                                          =                                    [                                                (                                      I                    ⁢                                                                                  ⁢                    M                    ⁢                                                                                  ⁢                    S                    ⁢                                                                                  ⁢                    I                    ⁢                                                                                  ⁢                    div                    ⁢                                                                                  ⁢                    K                                    )                                ⁢                mod                ⁢                                                                  ⁢                                  2                  k                                            ]                        +                          n              ×                              2                k                            ⁢                              (                                                      n                    =                    0                                    ,                  1                  ,                  2                  ,                  …                                )                                                                        (                  Equation          ⁢                                          ⁢          2                )            
In Equation 2, “Frame Offset” is given as 0 in the case of the FDD-based wideband code division multiple access schemes, and it has no effect on the position determination of the final paging occasion block. In Equation 2, “IMSI” (International Mobile Subscriber Identity) indicates a Non-Access Stratum (NAS) identifier for identifying the terminal, “K” indicates the number of Secondary Common Control Physical Channels (SCCPCH) of the physical channel including the paging channel (PCH), that is, the transport channel and “n” indicates a system frame number (Cell SFN). In addition, in Equation 2, “div” is given as an operator for returning an integer share with respect to a result of a division operation, and “mod” indicates modular arithmetic. The final paging indicator position of the specified terminal in the paging occasion determined in this manner is determined by Equation 3.PI(Paging Indicator)=(IMSI div8192) mod Np  EQUATION 3
In Equation 3, “Np” indicates the number of paging indicators for a paging indicator channel frame, and is determined by one of 18, 36, 72, and 144 according to the 3GPP specification. Particularly, “PI” is expressed in a format of a sequential Run for bit “11” or “00” and has a repeated structure by 8, 4, 2, and 1 times according to an Np value. Also, one PI may share at least one terminal according to the cell status, or may not use any terminal. When the PI is expressed in the repeated format of the bit “11”, it provides information that there is a paging message for the specified terminal among the terminals sharing the corresponding PI. Once a PI has been detected, the related terminals decodeds the next PCH frame transmitted on the Secondary CCPCH to see whether there is a paging message intended for them. If specified terminals find paging message intended for them, then finish the discontinuous reception operation and transition into the power active mode, CELL_FACH state. Otherwise, return to the discontinuous reception process of the power saving mode. When the PI has the repeated structure of the bit “00”, it provides information that there is no paging message of the base station for any terminals sharing the corresponding PI. In this case, all the terminals that have received the PI return to the discontinuous reception process without additional operations.
FIG. 2 illustrates one example of the discontinuous reception method in the case that □ is given as 3, IMSI is given as 77777, K is given as 5, n is given as 10, and Np is given as 18.
According to the discontinuous reception method for saving power in the 3GPP specification, the terminals obtain system information of the cell from the base station broadcasting message, and accordingly obtain a discontinuous reception cycle coefficient. In addition, according to Equation 1, Equation 2, and Equation 3, all the terminals of the cell determine whether to decode the paging information of Secondary CCPCH on the fixed PO with a constant interval without regarding various traffic characteristics and service requirements.
However, the terminals may face various time-varying traffic contents according to required QoS even in the same cell. And conventional discontinuous reception methods without considering of the power status of the terminals by base station may not improve the power saving performance. Accordingly, such a fixed discontinuous reception (FDRX: Fixed DRX) method may not efficiently support power saving of different terminals requiring various QoS.
Along this line, Korean Patent Application No 10-2000-0047204 “Channel communication method and apparatus of code division multiple access communication system” (2000.8.16) disclosed a method for transmission of Paging indicator matched with the discontinuous reception cycle in the code division multiple access communication system. However, it only has an effect on the capacity increase, and it includes a problem in that the power saving effect of the terminal is not provided.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.